Prophylactic Intravenous Phenylephrine 100, 150, and 200 Micrograms on Vasopressor Consumption, Bradycardia and Other Side Effects After Spinal Anesthesia in Obese Parturients During Cesarean Section: A Randomized, Single-Blind Study

Suchaya Jeeranukosol; Ratikorn Anusorntanawat

doi:10.33165/rmj.48.03.e272764

Authors

Suchaya Jeeranukosol Department of Anesthesia, Chaophrayayommarat Hospital, Suphan Buri, Thailand https://orcid.org/0009-0003-7125-9706
Ratikorn Anusorntanawat Department of Anesthesia, Chaophrayayommarat Hospital, Suphan Buri, Thailand https://orcid.org/0000-0002-6844-595X

DOI:

https://doi.org/10.33165/rmj.48.03.e272764

Keywords:

Cesarean section, Hypotension, Obese parturient, Prophylactic phenylephrine, Spinal anesthesia

Abstract

Background: Obese parturients require a higher effective dose at 50% of phenylephrine (P) for prophylactic infusion than non-obese parturients after combined spinal-epidural anesthesia. There has been no study on the optimal dose of P administered in obese parturients using slow injection with a smart pump imitation injection technique (SPIIT) to prevent spinal hypotension (SH).

Objectives: To compare vasopressor consumption, bradycardia, and other side effects between prophylactic P at doses of 100, 150, and 200 $\mu g$ intravenous slow injections after spinal anesthesia (SA) in obese parturients.

Methods: Participants were 369 obese parturients undergoing elective cesarean section (C-section) from December 2022 to June 2024 were randomized into P100, P150, and P200 (n = 123 per group). After completing SA, 3 groups were administered P at doses of 100, 150, and 200 $\mu g$ over 30, 45, and 60 seconds, respectively, by opening 3 ways of a 3-way stopcock to imitate the function of a smart pump. SH (systolic blood pressure [SBP] < 90% of baseline) was treated with P100 $\mu g$ .

Results: Mean rank of P were 201.0, 185.8, and 168.2 $\mu g$ in the P100, P150, and P200 groups, respectively (P = .03). Reactive hypertensions (HTs) (SBP > 110% of baseline) were 59 (48.0%), 61 (49.6%), and 87 (70.7%) in P100, P150, and P200, respectively (P < .001). Subgroup analysis showed SBPs higher than 130% of baseline were 2 (1.6%), 16 (13.0%), and 25 (20.3%) in P100, P150, and P200, respectively (P < .001). No significant differences were observed in other side effects.

Conclusions: The optimal prophylactic dose of P for management of SH with a SPIIT considering an acceptable incidence of bradycardia and reactive HT is 100 $\mu g$ after SA for C-section in obese parturients.

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